Design of SnO2:Ni,Ir Nanoparticulate Photoelectrodes for Efficient Photoelectrochemical Water Splitting

Currently, hydrogen generation via photocatalytic water splitting using semiconductors is regarded as a simple environmental solution to energy challenges. This paper discusses the effects of the doping of noble metals, Ir (3.0 at.%) and Ni (1.5–4.5 at.%), on the structure, morphology, optical properties, and photoelectrochemical performance of sol-gel-produced SnO₂ thin films. The incorporation of Ir and Ni influences the position of the peaks and the lattice characteristics of the tetragonal polycrystalline SnO₂ films. The films have a homogeneous, compact, and crack-free nanoparticulate morphology. As the doping level is increased, the grain size shrinks, and the films have a high proclivity for forming Sn–OH bonds. The optical bandgap of the un-doped film is 3.5 eV, which fluctuates depending on the doping elements and their ratios to 2.7 eV for the 3.0% Ni-doped SnO₂:Ir Photoelectrochemical (PEC) electrode. This electrode produces the highest photocurrent density (J_ph = 46.38 mA/cm²) and PEC hydrogen production rate (52.22 mmol h⁻¹cm⁻² at −1V), with an Incident-Photon-to-Current Efficiency (IPCE% )of 17.43% at 307 nm. The applied bias photon-to-current efficiency (ABPE) of this electrode is 1.038% at −0.839 V, with an offset of 0.391% at 0 V and 307 nm. These are the highest reported values for SnO₂-based PEC catalysts. The electrolyte type influences the J_ph values of photoelectrodes in the order J_ph(HCl) > J_ph(NaOH) > J_ph(Na₂SO₄). After 12 runs of reusability at −1 V, the optimized photoelectrode shows high stability and retains about 94.95% of its initial PEC performance, with a corrosion rate of 5.46 nm/year. This research provides a novel doping technique for the development of a highly active SnO₂-based photoelectrocatalyst for solar light-driven hydrogen fuel generation.

Implementation of Second-Generation Fourier Transform Electrochemical Impedance Spectroscopy with Commercial Potentiostat and Application to Time-Resolved Electrochemical Impedance Spectroscopy

We report the implementation of second-generation Fourier transform electrochemical impedance spectroscopy (2G FT-EIS) with commercial potentiostat. Although 2G FT-EIS based on chronoamperometry has several advantages of short measurement time and ability of time-resolved EIS, a special home-built electrochemical system is essential, which has been an obstacle to the wide application of 2G FT-EIS. Current commercial potentiostat and software, however, has sufficient power thanks to recent state-of-the art electronics and software industry. 2G FT-EIS requires two signals of time versus voltage and time versus current from chronoamperometry with a high sampling rate. In this work, auxiliary input of a commercial potentiostat was used to record voltage signal concomitant with typical chronoamperometry that consisted of time versus current. This simple approach enables the 2G EIS without expensive frequency response analyzer (FRA) and the complex home-built instrument. EISs with various charge transfer kinetics were investigated by the formation of a self-assembled monolayer (SAM) on Au with different chain lengths. More to the point, in situ time-resolved EISs during the SAM were obtained, demonstrating the ability of a commercial potentiostat for time-resolved EIS.